1. Field of the Invention
The present invention is generally concerned with so-called safety connectors, and is more particularly directed to safety connectors designed to be used in an explosive atmosphere.
2. Description of the Prior Art
As is known, connectors designed to connect selectively and electrically two cables, comprise, on the one hand, a female part, or socket, equipped, in addition to an optional ground receptacle, with at least two phase or neutral receptacles each connected to a respective conductor of a first of the cables and, on the other hand, a male part, or plug, equipped with pins which, connected to respective conductors of the second cable, are each designed to be engaged in a respective receptacle, to make the required electrical connection.
In an explosive atmosphere, and for obvious reasons of safety, it is important that the contact between the pins and receptacles takes place in an appropriately confined space, commonly referred to as an explosionproof safety chamber, so that if a spark is produced on such contact, either when the current is established or cut off, the explosion which may result is limited to the safety chamber, there being no propagation of the corresponding flame to the exterior of the latter.
At present, a safety chamber of this kind is common to all the receptacles of the socket.
A number of arrangements have been proposed, all of which presuppose mechanical latching of the plug to the socket.
According to a first of these arrangements, a bayonet type coupling is provided between the plug and the socket and, more often than not, there is also provided in the latter, in a separate compartment, for example, a switch which, placed on the input side of the receptacles, systematically disconnects the latter so as to permit the extraction of the plug and, inversely, to prevent its insertion when the receptacles are live.
In one variant, which is in practice permitted by the regulations only for sockets with a nominal rating below 10 A at 250 V, there is no switch of this kind but a shroud prevents direct access by the pins of the plug to the receptacles of the socket.
On insertion of the plug, rotation of it relative to the socket brings about its mechanical interlocking with the latter on the one hand and, on the other hand, either the closing of the switch utilized in the first case or the retraction of the shroud governing access to the receptacles of the socket in the second case.
In a second known arrangement, there is provided between the plug and the socket a key which governs the mechanical interlocking of the plug and the socket and which, by acting simultaneously on a switch situated in a separate compartment of the latter, closes or opens the connection on the input side of the receptacles.
In practice, arrangements of this kind result in relatively complex assemblies requiring a switch or shroud combined with a mechanical locking device, and are therefore relatively bulky and expensive.
A general objective of the present invention is an arrangement whereby these disadvantages can be overcome and in particular providing for automatic disconnection of the receptacles of the socket on removal of the plug without utilizing any form of switch or any form of shroud, and with no mechanical locking device.